This invention relates to an adjustable packing assembly for rotatable valve stems, and more particularly to such an adjustable packing assembly in which a predetermined compression of the packing against the stem is provided.
Heretofore, as shown in U.S. Pat. No. 4,940,208 dated July 10, 1990 a ball valve has been provided with packing about a stem for rotating a ball valve member between open and closed positions. Belleville washers or springs have been provided for exerting a compressive loading against a follower for the packing which in turn compresses the packing. The force exerted by the Belleville washers against the packing determines the compressive loading of the packing. While a desired compressive loading of the packing may be provided upon initial assembly of the ball valve, deterioration and excessive wear on the packing from prolonged use or possible exposure to corrosive fluids may reduce the compressive loading of the packing below a desired minimum.